Summary of Work: These studies are intended to generate data, using some widely-used and/or biologically-active pesticides, on the reproductive, immunologic, or neurologic systems in adult animals after developmental/perinatal/ juvenile exposure. This area was identified by the NAS in their book "Pesticides in the Diets of Infants and Children" as being an area of significant concern and few data. These studies are intended to partially fill those data gaps. Data on the first two compounds studied (methoxychlor and carbaryl) were shared with EPA immediately after completion. The effects stimulated an accelerated EPA review of the other currently registered organochlorine pesticides. Data have been collected for the third compound (chlorpyrifos) and are being analyzed. The next study (tebuconazole) is on-going. Overall, the data to date show that the adult effects of juvenile/perinatal pesticide exposure vary widely depending on the structure and range of biological activities of the pesticide. Some of the compounds tested have been without detectable consistent effects short of morbidity (i.e., there were no detectable changes even at doses that reduce pup viability), while others caused significant toxicities at doses that were previously found to be without effect when administerred to adults. For example, methoxychlor at the high dose in this study (150 mg/kg from gd14 to pnd42) caused adult sterility in females, and smaller testes and reduced sperm counts in males. The low dose (5 mg/kg) caused lower serum FSH and progesterone in females, although it was without detectable functional effect in adult femlaes (litter, gestation, and mating indices were not different from controls). Such effects were not observed for carbaryl.